Mustard gas, a nickname for a variety of sulphur mustard agents, was a class of related cytotoxic (ie toxic to cells) chemical weapons used primarily in World War I and World War II. The agents worked by preventing cellular division within the victim, leading to programmed cell death, DNA damage and, in some cases – where the victim survived the immediate effects – cancer in the long term.
In addition to the direct life-threatening capabilities of the gas, it was also a major irritant to the skin, eyes and respiratory system, leading to large yellow-fluid-filled blisters and chemical burns. Further, the gas had strong mutagenic effects on those it came into contact with, often resulting in severe disfigurement.
The gas was typically delivered onto a battlefield via artillery shells or, particularly in WWII, aerial bombs.
Today, the use, production and sale of mustard gas is strictly prohibited and, as such, it is not used in modern conflicts, with existing weapons either strategically destroyed or stockpiled within secure facilities.